Varistors
A varistor is an electronic component that has a voltage-current characteristic in which current flows when a certain voltage is reached. It is mainly used to protect semiconductors in electrics and electronic circuits from overvoltage. It has a structure where two electrodes sandwich a semiconductor ceramic with non-linear resistance characteristics. Varistors feature voltage and currents that are non-linear, and the current-voltage characteristics are symmetrical and have no polarity. The magnitude of the resistance changes depending on the voltage, and the lower the voltage, the higher the resistance, and the higher the voltage, the lower the resistance. At high voltage, the resistance of the varistor decreases and current flows, but the voltage drops due to the line impedance in the circuit. The varistor has performance such as surge current and energy resistance, excellent responsiveness, etc.